In order to improve the engineering characteristics (the geotechnical parametric values) of the ground underlying a building site prior to construction, specialist contractors referred to as Ground Improvement [hereinafter abbreviated to “GI”] contractors, operate on the ground using one or other of a variety of pieces of equipment specifically designed and built for this purpose. In many cases the GI contractor will select a machine which consists of a long cylindrical (pipe-like) tool such as the Vibroflot which has been in use since the 1930s. This long tool is sometimes referred to as a poker because of its shape and its use of agitation to improve the situation.
To treat the subject ground and improve its consistency to the depth required by the design engineer, the poker is inserted to an appropriate depth and then caused to exert forces on the soil around it, and in which it is embedded, while it is being withdrawn from the ground. In most cases the treatment force used is vibratory. In the particular case of equipment described in U.S. Pat. No. 6,554,543, the disclosure of which is incorporated herein by reference, the treatment forces are a combination of vibratory and hydrodynamic.